The Air Quality Study commissioned by Fort Worth to measure the impact of shale drilling on its air is a trove of important data (see earlier posting) and the consultants concluded that emissions to date caused no significant health impact.
But the study has a warning light for the Marcellus, as it reports that 8 compressor engines servicing production from 375 wells are emitting about 500 tons of nitrogen oxide per year or about 60 tons per engine.
The Marcellus air shed will not support 60 tons of nitrogen oxide per compressor engine. Pennsylvania's total nitrogen oxide emissions from all sources was about 180,000 tons in 2010. And that amount must decline substantially to comply with the Clean Air Act.
If one takes the ratio of compressor stations to gas wells of 1 engine for every 46 gas wells that is implied by the Fort Worth data, 3,300 Marcellus wells now drilled would require approximately 76 compressor stations and hundreds in the future.
This is rough, back of the envelope analysis, but hundreds of compressor stations plus more than a hundred drilling rigs, if each is running on the dirtiest fuels with least controls, could produce so much nitrogen oxide as to compromise meeting legally mandated air quality standards. Wyoming is now dealing with smog in counties where no smog existed as a result of drilling nitrogen oxide emissions. This problem is not hypothetical.
A compressor engine producing 60 plus tons of nitrogen oxide is likely running on diesel without the best pollution controls. The same engine running on electricity or gas with top pollution controls would emit about 5 tons per year.
The Clean Air Act's nitrogen oxide requirements can be met by deploying the clean engines and will not be met if the 60 plus ton emitters are installed throughout Pennsylvania.